## Forums Search for: IIR Filter

## two kinds of average filtering; exponential average VS modified moving average

in1. exponential average. (some kind of one order IIR filter) according to RC filtering and moving average. ,we can get the exponential average...

1. exponential average. (some kind of one order IIR filter) according to RC filtering and moving average. ,we can get the exponential average equ: yk=fs/(fs+2*pi*1.5*fc)*y(k-1)+(2*pi*1.5*fc/(fs+2*pi*1.5*fc))*xk ---yk, the current output ---fs, sampling frequency ---fc, the low pass filter (RC filter) cutoff frequency 1.5*fc to make it in the passband for pratical caclulation. advanta...

## IIR fillter implementation

inHi group, Can anyone help me on implementing the iir filter in lattice ladder structure. I want to implement in FPGA. Since lattice ladder is...

Hi group, Can anyone help me on implementing the iir filter in lattice ladder structure. I want to implement in FPGA. Since lattice ladder is robust at finite word length i want to explore it to full. Even dsp implementation views will do i will convert it to VHDL myself. Thanks in advance Amit

## Winfilter bug?

inHello all, I think there may be a bug in the Winfilter08 program. However, the bug which I will state below, is really too obvious so I am...

Hello all, I think there may be a bug in the Winfilter08 program. However, the bug which I will state below, is really too obvious so I am doubting myself. Anyway, hear goes: In the C code generation of an IIR filter (lowpass, 8th order, chebychev, fs=1000Hz, fcut1=250Hz, Ripple=1dB), I think that there is an error that gets generated when the fixed point (16 or 8bit) is chosen. Th...

## Oversampling using Cheby2 IIR FIlter.

inI have to use a cheby2 IIR filter with 60db bandstop ripple to implement oversamplig procedure. I'm sure that I can calculate the coefficient...

I have to use a cheby2 IIR filter with 60db bandstop ripple to implement oversamplig procedure. I'm sure that I can calculate the coefficient with matlab in few minutes, but in my application I have to calcute it in real time depending on the cut-off frequency. My question is: thers is an analitic rappresentation of the transfer function of cheby2 filter dapending on the frequency in lapl...

## IIR filter implementation in C

inHi all, I have designed an algorithm in MATLAB, and am currently trying to translate it into C code so that I can run it in real time. At the...

Hi all, I have designed an algorithm in MATLAB, and am currently trying to translate it into C code so that I can run it in real time. At the moment I am stuck on the IIR filter. I am trying to implement the function [B,A] = cheby1(4,1,[80/48000,16000/48000],'bandpass') I have found two promising sources online that provide source code for an IIR filter in C: 1) http://www-users.cs.york....

## IIR filter question

inHi Guys, I was asked to review a potential article for the IEEE Sig. Proc. magazine. In that article the author implies that IIR...

Hi Guys, I was asked to review a potential article for the IEEE Sig. Proc. magazine. In that article the author implies that IIR (recursive) filters aren't as popular nowadays as they were in the past (say 10-20 years ago). Now I'm no IIR filter designer, so I need your opinions. Aren't IIR filters still as popular now for audio signal processing as they were 10 years ag...

## Analog to digital IIR filter

inHi all I know this topic has been discussed at several levels in this group before. Tim Wescott even worked out a similar scenario with me a...

Hi all I know this topic has been discussed at several levels in this group before. Tim Wescott even worked out a similar scenario with me a few months back...but either I'm really bad at algaebra or I'm missing something. I'd appreciate if some of you can help me find the problem My goal is to model a simple 'charge' circuit using a digital filter. In the time domain, I guess you can de...

## Linear phase IIR filter

inHello, I am currently designing a decimating filter for a sigma delta converter. I am searching a small decimating filter. I heard about...

Hello, I am currently designing a decimating filter for a sigma delta converter. I am searching a small decimating filter. I heard about approximately linear phase iir filter. Where can I find some implementation examples? Thanks you in advance Thoma

## An IIR filter gain questio

inHi Guys, I have a (probably simple) question about "scaling" the coeffs of an IIR filter. I've been workin' on an simple...

Hi Guys, I have a (probably simple) question about "scaling" the coeffs of an IIR filter. I've been workin' on an simple 2nd-order biquad filter that takes the standard form: x ---> (+)-----> ----------b0-----> (+)---> y ^ | ^ | [z^-1] | | | | (+) (+) ^

## DSP Riddle: Infinitely Narrow Notch Filter

inFolks, is it possible to construct a causal and realizable n-th order IIR filter, where n > 1 is an integer, which acts as an infinitely...

Folks, is it possible to construct a causal and realizable n-th order IIR filter, where n > 1 is an integer, which acts as an infinitely narrow notch filter? This filter must have frequency response H(w) = 1, for w =/= w0 = 0, for w == w0, for some arbitrary 0 < w0 < pi. Assume for the moment that the filter can be computed with infinite precision. Have a nice weekend!

## amplitude change in time variable iir filter

inHello, If I change the coefficients of an iir filter with the intention to change the resonance frequency, this will also change the...

Hello, If I change the coefficients of an iir filter with the intention to change the resonance frequency, this will also change the amplitude. How can I modify the values in the filter taps to compensate for the amplitude change. example: A 2 pole filter with pole on the unit circle: C = 2 cos(freq); y[k] = C y[k-1] - y[k-2] I hit this filter with an impulse and...

## using IIR filter library for C2000 DSP

inHi, I wanna implement a low pass IIR filter in C2407 using the 24x Filter library. I am a new comer to this kind of implementation. ...

Hi, I wanna implement a low pass IIR filter in C2407 using the 24x Filter library. I am a new comer to this kind of implementation. /*After the initation:*/ { iir.dbuffer_ptr=dbuffer; iir.coeff_ptr=coeff; iir.qfmat=IIR_LPF_QFMAT; iir.nbiq=IIR_LPF_NBIQ; iir.isf=IIR_LPF_ISF; iir.init(&iir); } while(ADUPDATE) /*new adc coming*/ { ...

## a question on IIR low pass filter

inone low pass IIR filter is implemented on a fixed-pointed DSP, say, TI C5402. The IIR filter itself is stable. IF the input to the filter is...

one low pass IIR filter is implemented on a fixed-pointed DSP, say, TI C5402. The IIR filter itself is stable. IF the input to the filter is one constant value (DC signal ), eg, X input= 1000; so, afte the stabilization, the output from the IIR filter is also 1000? or some value less than 1000? Actually, I just wonder that the output will be less than 1000 because of the finite w...

## Implementing cascade IIR filters

inDear comp.dsp, I am just beginning my foray into practical DSP after learning the bookish stuff in class. To try out various things, I...

Dear comp.dsp, I am just beginning my foray into practical DSP after learning the bookish stuff in class. To try out various things, I manipulating wave files in C, and in parallel, trying to make XMMS (http://www.xmms.org) effect plugins to get the effect in real time. My query is about IIR filtering. What is the best way to implement an IIR filter, assuming that I get data in blocks o...

## changing the frequency of an IIR filter knowing only its coefficients

inwe are here in a case where only the coefficicents of the IIR filter are known. Is it possible to change the cutoff frequency of this filter...

we are here in a case where only the coefficicents of the IIR filter are known. Is it possible to change the cutoff frequency of this filter (which could be a notch filter for example, or something more complex) having only its coefficients (a0/a1/b1...)? 1- can any filter of any pole (2 to 16 and more) be transformed back into a pole-zero notation? If yes, would there be then any chance tha...

## constraining the filter to be stable using matrices

inHello all, How to put the constraint that the IIR filter which I design, is always stable using matrix notation? thank you sri hari

Hello all, How to put the constraint that the IIR filter which I design, is always stable using matrix notation? thank you sri hari

## design an iir by time-domain impulse response

inHi, I wonder if there are methods to calculate the coefficients of a recursive iir filter, for a given time-domain impulse response. (Of...

Hi, I wonder if there are methods to calculate the coefficients of a recursive iir filter, for a given time-domain impulse response. (Of course I can not give an infinite impulse response, but if I want a filter which follows approximately the given impulse response of maybe 16 samples or so - it can have an additional 'tail' afterwards) I wonder if this might be usefull for the implem...

## FPGA

inHi, I have designed a IIR filter which is formed of 14 2nd order cells. I'd like to make it work on a FPGA. I've seen that differents forms...

Hi, I have designed a IIR filter which is formed of 14 2nd order cells. I'd like to make it work on a FPGA. I've seen that differents forms of cells do exist (direct, form 1, form2...). I'd like to know which one is better for a FPGA. Any piece of advice is welcome ! Thanks a lot for your help. S.

## generating stable IIR filter?

inHi, I am trying to generate an IIR filter from an H(s) and having difficulty stabilizing it. The H(s) in question is documented...

Hi, I am trying to generate an IIR filter from an H(s) and having difficulty stabilizing it. The H(s) in question is documented here: ftp://ftp.iol.unh.edu/pub/ethernet/test_suites/CL25_PMD/PMD_Test_Suite_v3.4.pdf on page 44 equation 25.C-5. It defines a high pass system as it's two transformers with a piece of cable in between so when the cable is short transformers block all DC. I used the...

## calculating the coefficients of a butterworth iir filter

inHallo everyone! I wanted to ask your advice on the following problem: i have to generate a butterworth iir bandpass filter with...

Hallo everyone! I wanted to ask your advice on the following problem: i have to generate a butterworth iir bandpass filter with cutoff frequencies of 0.008 and 0.05 Hertz. This will be used in filtering a time signal sampled at 1 Hz (so the sampling frequency is high enough to work with the time signal) My initial problem is to calculate the coefficients. Ive thought of a few ways to cal...